Pavement construction

ABSTRACT

An improved pavement construction is provided wherein the pavement foundation includes a layer of resilient material to give increased resistance to cracking. As a subcombination, a pavement is disclosed including a layered asphaltic concrete improved by the addition of various scrap or waste materials. This abstract is not to be construed in any way to define or limit the invention set forth below.

United States Patent 11 1 1111 3,850,537 Bynum, Jr. Nov. 26, 1974 [5PAVEMENT CONSTRUCTION 1,629,487 5/1927 01611116116 404/44 x 2,875,0842/1959 P tt 404 17 X [76] Invent Dwghs Bynum, 17511 Lormg 3,038,3926/1962 404144 x LIL, Houston 77040 3,577,893 5/1971 Towner 404/313,577,894 5/1971 Emerson, Jr.... 404/31 [22] 1972 3,603,221 9/1971Barton 1. 404 31 [2]] Appl. No.: 302,422

Primary Examiner-Nile C. Byers, Jr. 52 us. c1. 404 17 Attorney, "1Ronald Robins; Joe 51 1111.01. E016 11/00 Edwards [58] Field of Search404/17, 27, 18, 28, 82,

404/31 321 44 57 ABSTRACT 5 References Cited An improved pavementconstruction is provided UNITED STATES PATENTS wherem the pavementfoundation includes a layer of resilient material to give increasedresistance to crackroffel 26 3 ing. As a subcombination, a pavement isdisclosed in- 622877 411899 ig 'g 4/44 X eluding a layered asphalticconcrete improved by the 6542]6 7/1900 404/72 X addition of variousscrap or waste materials. This ab- 656:094 8/1900 Decaiimte'r'g"IIII'IIIII'.1.. 260/758 5mm is not to be construed in anyWay define or 674,823 5/1901 Amies 106/126 limit the ion set forthbelow.

1.4] 1,786 4/l922 Hopkinson 404/32 X 1,611,330 12/1926 B1111 404/2s x 5Clams, 3 D'awmg F'gures Y//// '.o" NF Z2 1 PAVEMENT CONSTRUCTION Thepresent invention relates to pavement constructions, and morespecifically to pavement constructions improved by the utilization ofnormally waste or scrap solid materials. In one embodiment, variouswaste materials are utilized to provide a resilient layer in pavementfoundation to yield improved crack resistance in the foundation. Wherethe pavememt is utilized as a roadway, or the like, it may include oneor more layers of flexible concrete (also called asphaltic concrete orblack top), and various improved'flexible concretes are disclosedutilizing normally waste materials for improving the strength,flexibility, elongation and thermal durability of the concrete.

Referring now to the drawings, wherein preferred embodiments of theinvention are illustrated, and wherein like numerals illustrate likeparts:

FIG. 1 is a view in elevation showing a cross-section of pavementconstruction, illustrating the various layers including the resilientlayer according to one embodiment of the present invention.

FIG. 2 is a plan view of the resilient layer of FIG. 1.

FIG. 3 is a schematic illustration in side elevation of a tire showinghow it might be cut to be utilized'in the pavement of FIG. 1.

FIG. 4 is a view in elevation showing a cross-section of pavementutilizing an alternate form of resilient layer. v

FIG. 5 is a perspective view partly in section of a pavementconstruction utilizing blocks of scrap material in the resilient layer.

FIGS. 6 and 7 are perspective views partly in section of pavementconstructions wherein the resilient layers comprise a matrix of theresilient material and a nonresilient material such as sand.

FIG. 8 is an enlarged fragmentary view in sectional elevation of aflexible concrete which may be used in the pavement constructions ofFIGS. 1 and 4-7.

A principal problem withpavements and foundations, whether utilized asbuilding foundations or as roadways, sidewalks and the like, is thetendency of the pavement to crack due to movements of the underlyingearth. Such earth movements are typically caused by temperature andmoisture variations, subsistence, and the like. It has been found thatsuch foundation cracking can be greatly retarded by the use of a layerof resilient material in the foundation between the base and surfacelayers of the foundation to absorb movement of the base layer withouttransmitting those movements to the surface layer and to retard thepropagation of cracks from one layer to another.

Referring now to FIG. 1, there is shown in crosssection a pavementconstruction comprising various layers. At the bottom is the grade, orcompacted earth, 10 above which is a base layer 12. The base 12-may beof any suitable material such as Portland concrete or' asphaltic(flexible) concrete. Also, the base 12 may be newly laid or may be anold roadway which has been resurfaced. Above the base 12 is a resilientlayer 14,

the construction and function of which are described. in greater detailhereinafter. Above the resilient layer 14 is an upper layer 16 also ofasphaltic or Portland concrete. A final surface course 18 may also beprovided for a very smooth upper surface for the pavement or forwaterproofing or the like. The pavement illustrated in FIG. 1 may serveas the pavement for a roadway or sidewalk, or for a building foundation.As discussed, principal problem with such pavements is the-tendency ofthe pavement to crack due to movements of the earth 10 below thepavement due to changes in temperature, moisture content, subsistenceand similar causes. Such movements cause alternate stretching andcompression of the overlying pavement. Under such circumstances,cracking of the upper layer 16 may typically result from two causes.First, horizontal movements of the underlying earth cause stretchingand/or buckling which eventually cracks the pavernent base 12. Such acrack in the base isillustrated at 20. It is well knownthat such cracksin materialwilltendto propagate through the material upon repeatedstresses, untilmovements in the underlying earth, preventing thosemovements from being transmitted into the upper layers where they wouldcause defonnation and cracking of the pavement surface.

In the preferred form, the resilient layer 14 comprises an array of tirerings 22 embedded in compactedsand 24. As shown in FIG. 3, the tirerings are provided by cutting the tire around its perimeterperpendicular to the axis. As shown, two cuts are preferably made sothat the resulting circular sections or rings will be sufficiently thinto be buried in the sand without necessitating too thick a layer ofsand. The center sections of the tires may be ground up for use as anadditive to the asphaltic concrete, as described hereinafter. Informingthe resilient layer 14, according to FIGS. 1 and 2, a layer of sand isfirst spread over the base 12 and the tire rings 22 placed in the sandin a grid pattern or'array such as that illustrated in FIG. 2,preferably with-the concave surfaces oriented upwardly as illustrated inFIG. 1. More sand is spread, covering the tires, and the whole layercompacted before the upper pavement layer 16 is poured.

Referring now to FIG. 4, thereis shown an alternate pavementconstruction wherein the resilient layer is formed of shredded wastemetalcans. Thereover the grade or earth 10 is provided the base layer 12which may be a newly laid base-layer of Portland or asphaltic concrete,or which may be an old'roadway which has cracked or buckled. Over thebase: layer 12 is poured a thin coating 26 of bitumen, or otheradhesivebinder. A layer of shredded and somewhat compacted metal cans 28is placed over the adhesive coating 26 to form the resilient layer forthe pavement. Another coat of bitumen 26 may be placed on top of thecompacted shredded metal cans 28, followed by the upper pavement layer16.

Another alternate embodiment is illustrated in FIG. 5 wherein theresilient layer 14 is formed from blocks or' cubes 30 of compressedwaste material, such as waste paper, which may also include othershredded waste materials, such as rubber, plastic, cloth, etc. The

blocks are formed by application of high pressure on a mold filled withthe scrap paper or other waste material. The block holds its shapebetter if granulated plastic is mixed with the paper and the block isthen heated so that the plastic will soften and fuse the paper together.Other binder for the paper or coating for the blocks may of course beused as desired. Although the blocks 30 may be of any desired shape,cubes of approximately 2 inches to a side, or larger, are preferredbecause of their ease of placement. Where blocks or cubes are utilizedas illustrated in FIG. 5, it is also desirable to have layers 26 ofbitumen or other adhesive on either side of the resilient layer 14 tobind the cubes to the upper and lower pavement layers 12 and 16.

If desired, the resilient material utilized in the resilient layer 14may be dispersed in a matrix with nonre silient material such as sand.Such a construction is shown in FIG. 6, wherein the resilient materialis arranged in strips 32 alternating with strips of sand 34. FIG. 7shows the resilient material as an array of islands 36 in a sea of sand38. Alternatively, the sand could be provided in islands surrounded by asea of resilient mixture. Numerous resilient materials are suitable forthe present invention, but it is preferred to use normally scrap orwaste solid material such as shredded tin cans, ground rubber, bark,sawdust or other ground wood.

Where the upper pavement layer 16, or, if provided, the surface course18, is of flexible or asphaltic concrete, commonly referred to as blacktop, it has been found that the concrete can be improved by theincorporation of various types of waste solid matter. For

The use of ground rubber in the asphalt mix also improves the flexibleconcrete by making it more resilient. The rubber may be convenientlyobtained by grinding or shredding scrap tires. One percent or more byweight of rubber is effective in improving the pavement and up to 50percent by weight may be used.

When making asphaltic concrete, dirty aggregate, such as gravel, iswashed and dried before mixing with the asphalt or other binder so thatgood adhesion between the binder and the aggregate is achieved. If goodadhesion is not obtained and the concrete is being used as an outdoorsurface course, then water will seep around the rocks and causedeterioration of the binder. However, at the same time, poor adhesion ofthe binder to the rock will result in greater elongation capability inthe asphaltic concrete and make it less liable to cracking. Therefore,an asphaltic concrete utilizing a usually asphalt or tar, mixed withvarious sizes of crushed rock or gravel aggregate. It has been foundthat this type of flexible concrete can be improved by the substitutionof crushed or ground glass for part or all of the usual rock aggregate.The glass can be obtained from scrap glass containers, crushed in a jawcrusher or ground in a ball mill. The use of crushed glass results inmore long splinters or slivers of glass which give the asphalt increasedskid resistance. The greater the proportion of glass substituted for theusual rock aggregate, the greater the resistance of the concrete tothermal distress. Flexible concrete formulated with glass shows lessexpansion and contraction due to temperature changes, than doesconventional flexible concrete.

According to another aspect of the present invention, lab tests haveindicated the desirability of plastic additives in the flexible concreteto improve the adhesion and cohesion. The addition of thermoplasticmaterial to the mixture would also tend to decrease chemical aging ofthe asphaltic concrete due to cross-linking with the asphalt.Thermoplastic materials are utilized since they deform or melt uponheating. Thennal plastic waste materials, such as plastic bottles or thelike, may be shredded or ground and added to the hot asphalt or hotaggregate prior to or during the mixing of the two to form the concrete.The heat of the asphalt or aggregate will melt the plastic and themixing of the concrete disperse the plastic throughout the mixture.Thermoplastic material may be effective in an amount as small as 0.1percent by weight based on the entire weight of the concrete mixture,and may be used in any amount up to about 10 percent by weight.

dirty or a coated aggregate will yield superior pavement if protectedwith a thin waterproof layer, or if the quality of the binder isimproved as by adding of the scrap thermoplastic material as describedabove.

An asphaltic concrete utilizing a dirty or coated aggregate isillustrated in FIG. 8. There the aggregate particles 40 have a surfacecoating 42 of some material such as dirt which does not adhere tightlyto the aggregate. The binder or asphalt 44 is therefore prevented fromadhering tightly to the aggregate, permitting the aggregate to moveslightly in the binder so that the concrete can expand or flex to agreater extent without the formation of cracks. The coating 42 need notbe continous, however, and may be discontinuous at spots such as at 46,permitting the binder to adhere to the aggregate sufficiently to holdthe concrete together.

While the aggregrate coating 42 may simply be dirt adherring to theaggregate, it may also be a synthetic coating deposited on cleanaggregate such as clean rock or gravel, or the crushed glass describedabove. One such coating material which has been found satisfactory ispulp paper. The paper may be scrap or new, and may be added to theaggregate by mixing the paper pulp with the aggregate, or by droppingthe aggregate through pulp and then allowing the aggregate to dry.

Another synthetic coating for the aggregate may be latex rubber derivedfrom any suitable source. The rubber may be mixed with the hot aggregateto coat it prior to mixture of the aggregate with the asphalt or otherbinder.

Reinforcement of asphaltic concrete has been recognized as desirable,but is too expensive to utilize in general practice. However, it hasbeen discovered that reinforcement of the asphaltic concrete by theaddition of grass or animal manure, will greatly improve both thestrength and elongation characteristics of the concrete. FIG. 8 showssuch fibers 48 in the concrete.

A fiber-reinforced asphaltic concrete according to the invention maycomprise approximately 3% to 12 percent by weight asphalt, or otherbinder material, and approximately 0.1 to 15 percent by weight of f1-brous reinforcing material, with the remainder comprising aggregate suchas crushed rock, gravel, ground glass, etc. A portion or all of theaggregate may be coated as above described.

It is apparent that other asphaltic concretes may be provided by aplurality or all of the above features, that is, where shredded tiresand scrap plastic are added to the asphalt binder, together with scraprags, manure, straw, hay, etc., and wherein the concrete aggregate iscrushed or ground glass. The sublayers of the overall pavement mightalso utilize scrap tires, tin cans, waste paper, etc. as indicatedabove. The use of such paving constructions would result not only inimproved pavements, but also would greatly reduce the problem of solidwaste disposal.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof and various changes in the size,shape and materials, as well as in the details of the illustratedconstruction, may be made within the scope of the appended claimswithout departing from the spirit of the invention.

What is claimed is:

1. In a pavement construction of the type including upper and lowerlayers of concrete, the improvement comprising: 7

an intermediate layer, disposed between said upper and lower layers,said intermediate layer being formed of a matrix of rubber tire ringsembedded in sand.

2. The pavement according to claim 1 wherein said tire rings are formedfrom whole tires cut about their perimeters perpendicular to their axesto form a plurality of annular sections.

3. The pavement according to claim 1 wherein said tire rings aredisposed in said sand with their concave surfaces oriented upwardly.

4. A pavement comprising,

upper and lower layers of concrete with an intermediate layer ofshredded metal cans. 5. The pavement of claim 4 wherein said metal cansare held in place with an adhesive binder.

1. IN A PAVEMENT CONSTRUCTION OF THE TYPE INCLUDING UPPER AND LOWERLAYERS OF CONCRETE, THE IMPROVEMENT COMPRISING: AN INTERMEDIATE LAYER,DISPOSED BETWEEN SAID UPPER AND LOWER LAYERS, SAID INTERMEDIATE LAYERBEING FORMED OF A MATRIX OF RUBBER TIRE RINGS EMBEDDED IN SAND.
 2. Thepavement according to claim 1 wherein said tire rings are formed fromwhole tires cut about their perimeters perpendicular to their axes toform a plurality of annular sections.
 3. The pavement according to claim1 wherein said tire rings are disposed in said sand with their concavesurfaces oriented upwardly.
 4. A pavement comprising, upper and lowerlayers of concrete with an intermediate layer of shredded metal cans. 5.The pavement of claim 4 wherein said metal cans are held in place withan adhesive binder.